1. Field of the Invention
This invention concerns a method and system to prevent the formation of an electrical arc on a connector inserted into a supply line of a power load, particularly applicable to a network installed in an automobile to supply power loads, such as a 42V network in a vehicle with two voltage levels (14V and 42V, or “dual voltage” system) with the aim of preventing, when the connector components become separated either accidentally or due to a lack of warning from a manipulator, an electric arc from being generated between contact points which causes the premature destruction or deterioration of these contacts, or of the connector itself, an untimely interruption in the supply to certain loads of the network or a fire situation with damage of varying degrees of seriousness, particularly during the disconnection of the two components or electroinsulator support components of a connector carrying the contact electroconductive terminals.
The invention is also of special interest for electrical vehicles in which a group of batteries is used to provide energy for an electrical engine used to propel the vehicle and where the current levels are in the order of 400 A to 400 V, for C.C., and from 40 A to 220 V for C.A., whose current and voltage levels require the incorporation of a series of safety measures to minimize the risk of injury for the users, mechanics and safety technicians.
2. Background of the Invention
The gradual implementation of the supply system on two different voltage levels in an automobile means that one part of the network, particularly that used to supply power loads, is supplied at a new voltage level, for example 42V, much higher than the voltage of approximately 14V commonly used in automobiles up to now. It is obvious that the supply of loads at this new higher voltage level provides some clear advantages. However, it also has the disadvantage of being high enough to generate electrical arcs, particularly when connectors in lines that supply loads at this high voltage are disconnected.
Also in electrical traction vehicles, whose gradual implementation is foreseeable, supply currents at high levels are used which are liable to generate electrical arcs.
There are numerous documents dealing with the problem of the formation of an electrical arc, both when connecting and, particularly disconnecting the two parts that make up a connector inserted into a load supply network at a voltage level liable to generate these electrical arcs.
In EP-A-697751, EP-A-673085 and U.S. Pat. No. 6,146,160 connectors are described with the means for an efficient mechanical subjection of the connection terminals, normally electroconductive bolts and eyebolts, so that accidental disconnection cannot occur.
In U.S. Pat. No. 3,945,699, U.S. Pat. No. 4,749,357 and U.S. Pat. No. 5,676,571, the means linked to the receiving nut of electroconductive bolts are described, intended to obstruct or minimise the formation of electrical arcs when connecting the two components of a connector.
U.S. Pat. No. 6,225,153 describes a universal load gate connector for electrical vehicles, where a mechanism is provided to cut the current liable to generate an arc during disconnection of the male and female terminals of the connector before the uncoupling of the two component parts of the connector, in particular to prevent the disconnection of the connectors during the charging of the vehicle batteries, whose mechanism includes a mechanical lock of these two parts activated by a trigger which is linked to a switch connected to a power source for the whole of the connector. Through this switch, and on the trigger being activated by a user, the current circulation towards the power load to be supplied is disabled before the disconnection of the male-female terminal or power terminals of the connector is enabled.
U.S. Pat. No. 5,542,425 describes an instrument and method for preventing the deterioration of contacts in electrical equipment, specifically in equipment for acquisition of images with an ultrasound system in which several probes can be connected to the acquisition system without the risk that when disconnecting these probes an electrical arc will be given off, in whose system the connector includes a part activated mechanically to activate and deactivate a connection interface between the components, including a sensor or detector which determines when the connector is going to be disconnected by one of the components and provides a signal which is used by one of the components to disable the electrical energy supply towards the connector and thus prevents the formation of an electrical arc when the male-female terminals of the same separate physically. In the different examples that this patent illustrates the aforementioned part is a gyrating shaft on which the user must act and the aforementioned sensor is an optical sensor, magnetic sensor or a simple switch.
In the last two cases, the disconnection of the supply source is carried out either by the user himself (as in U.S. Pat. No. 6,225,153) or through the addition of a sensor linked to a mechanism also activated by the user (as in U.S. Pat. No. 5,542,425), the connector always being required to act with the means to appropriately displace its contacts, generation of delays by the operating mechanical conditions being essential for its adequate operation.
One objective of this invention is to provide a method for preventing the formation of an electrical arc in a connector inserted in a supply line of a power load making use of specific characteristics of the falls in voltage and evolution of the intensity which occur when a disconnection of the supply to a power load is carried out in order to detect the moment of disconnection and cut the supply of electrical fluid to this load before an electrical arc can occur.
Another objective of this invention is to provide a system to implement a method with the characteristics described in the previous paragraph with a low cost and based on components currently in use, particularly in the automobile industry.